Fault Description: iPhone 6 Wi-Fi can't be turned on while displays grey.
Possibility Reason: The Wifi IC happens something abnormal.
We have tested the Wi-Fi, it really doesn't work, so the ICs may happens what we have doubted like that.
For this problem, first we can replace the iPhone WIFI IC directly. After install the iPhone WIFI IC, turn on iPhone 6, but it stuck when it entering the Settings, so the problem isn't been solved. Next remove the iPhone WIFI IC and test several key point signals, we found the 14 pin doesn't has the resistance value. Now, we need to check iPhone CPU, it's complicated.
Pic 1
There is no Bus reset signal, the normal is 1.8V, we are going to borrow it from another place, and there is a 1.8V beside it.
Pic 2
It's useless if we directly connect it, so we need to find a resistor to pull it up. Put iPhone motherboard under the Stereo Zoom Microscope, and then remove a boot signal pull-up resistor 220K,
Pic 3
Install the iPhone WIFI IC, and then turn on the iPhone to test, now the iPhone WIFI function can be used normally.
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